In the telecommunication field, an operator provides subscribers with broadband telecommunication services and narrowband telecommunication services at the same time through the local telephone electric cable, usually the twisted pair. For example, the Asymmetric Digital Subscriber Line over the Plain Old Telephone Service (ADSL over POTS), the ADSL over the ISDN, the Very high bit-rate DSL over the POTS (VDSL over POTS), and the VDSL over the ISDN. These applications are very universal, and the xDSL is the joint name of the ADSL and the VDSL.
As shown in FIG. 1, the xDSL signal and the POTS/ISDN signal coexist in one subscriber line. In the office end, the voice Splitter (SPL) in the broadband access device Data Subscriber Line Access Multiplexer (DSLAM) is adopted to differentiate the broadband services from the narrowband services, and send them to the broadband service panel (namely, xDSL service panel) and the narrowband service panel (namely, POTS/ISDN service panel) to be processed respectively. In the subscriber end, the Splitter (SPL) sends the separated broadband service and narrowband service to the Remote Terminal Unit (RTU) and the telephone. During the process of service operation and maintenance, it is usually necessary to take various measurements of the subscriber communication line to detect the quality and failure of the communication line. The broadband communication line detecting device in FIG. 1 is a device for implementing various testing functions.
To improve the quality of the voice signal transmission, at least one coil is usually connected in series to the communication line; however, when the xDSL service is put into operation, the existence of the coil will impact the operation of the xDSL service. Therefore, the coil needs to be removed from the communication line to support the operation of the xDSL service. Accordingly, how to decide whether there is a load coil on a certain communication line is very important for an operator to implement the intelligent maintenance on the communication line. At the same time, when detecting the failure, the office end usually needs to know whether the SPL in the office end or the subscriber end have been mounted correctly. How to decide whether the SPL has been mounted correctly is also a key for implementing the intelligent maintenance on the communication line.